CGI::Fast is a subclass of the CGI object created by CGI.pm. It is specialized to work well with the Open Market FastCGI standard, which greatly speeds up CGI scripts by turning them into persistently running server processes. Scripts that perform time-consuming initialization processes, such as loading large modules or opening persistent database connections, will see large performance improvements.

In order to use CGI::Fast you'll need a FastCGI-enabled Web server. Open Market's server is FastCGI-savvy. There are also freely redistributable FastCGI modules for NCSA httpd 1.5 and Apache. FastCGI-enabling modules for Microsoft Internet Information Server and Netscape Communications Server have been announced.

In addition, you'll need a version of the Perl interpreter that has been linked with the FastCGI I/O library. Precompiled binaries are available for several platforms, including DEC Alpha, HP-UX and SPARC/Solaris, or you can rebuild Perl from source with patches provided in the FastCGI developer's kit. The FastCGI Perl interpreter can be used in place of your normal Perl without ill consequences.

You can find FastCGI modules for Apache and NCSA httpd, precompiled Perl interpreters, and the FastCGI developer's kit all at URL:

FastCGI scripts are persistent: one or more copies of the script are started up when the server initializes, and stay around until the server exits or they die a natural death. After performing whatever one-time initialization it needs, the script enters a loop waiting for incoming connections, processing the request, and waiting some more.

A typical FastCGI script will look like this:

#!/usr/local/bin/perl # must be a FastCGI version of perl!
use CGI::Fast;
&do_some_initialization();
while ($q = new CGI::Fast) {
&process_request($q);
}

Each time there's a new request, CGI::Fast returns a CGI object to your loop. The rest of the time your script waits in the call to new(). When the server requests that your script be terminated, new() will return undef. You can of course exit earlier if you choose. A new version of the script will be respawned to take its place (this may be necessary in order to avoid Perl memory leaks in long-running scripts).

CGI.pm's default CGI object mode also works. Just modify the loop this way:

while (new CGI::Fast) {
&process_request;
}

Calls to header(), start_form(), etc. will all operate on the current request.